The disclosure relates generally to measuring landing gear loads and calculating aircraft gross weight using fiber optic sensors on landing gear, and more specifically, to de-coupling multiple mechanical and thermally induced strain measurements into their mechanical and thermal components to accurately measure a load on the landing gear.
In general, fiber optic sensors bond to a mechanical structure to sense a total strain by measuring a shift in wavelength of reflected light caused by mechanical strain in the mechanical structure. The total strain is composed of a mechanical strain (load) and a thermally induced strain. For example, when measuring a load in an landing gear, the changes in altitude subject the landing gear to thermally induced strain caused by changes in temperature at different altitudes. To accurately measure the load, the mechanical and thermally induced strain must be isolated from each other.
Current methodologies do not differentiate well between these two strains, especially in changing thermal conditions (e.g., which is the case when an aircraft descends for landing). Further, present thermal compensation can be affected by thermal sensor accuracy, geometry, and thermal bulk of the mechanical structure.